DI Cass Jones (ex-undercover, takes kickbacks and occasionally drugs, but not an overly bad man) is working two cases: the accidental gangland shooting of two schoolkids, and a serial killer investigation - when his younger brother, a successful accountant working for a subsidiary of The Bank, shoots his wife and son before committing suicide himself, leaving only a confused note that makes no sense. It's not long before Cass's affair with his brother's wife comes out. Then test results show that he had sex with her only hours before her death . . . and his fingerprints are on the shotgun.